How does the Source know the dongle plug in? because the VBUS is not powered, and CCG3 is not working, so the Rd is not available.
I'm looking throngh the reference design on this page: http://www.cypress.com/documentation/reference-designs/ez-pd-ccg3-usb-type-c-displayport-cable-solution
CCG3 have Rd_DB which is means CCG3 support dead battery Rd. The Rd will present on CC line when CCG3 is not powered.